In general, a bandwidth available in an IP network (hereinafter, referred to as an available bandwidth) is an unused bandwidth subtracting the other traffic (hereinafter, referred to as cross traffic) flowing over the IP network from the physical bandwidth of an IP network. For example, when the physical bandwidth is 100 Mbps and the cross traffic is 30 Mbps, the available bandwidth is 100 Mbps−30 Mbps=70 Mbps.
Various proposals for a measuring technology of an available bandwidth has been made in the past. For example, Non-Patent Literature 1 discloses a technique of transmitting the train of plural measurement packets in a fixed size as a collection from a transmitter terminal to a receiver terminal, and causing the receiver terminal to detect a change in the receiving interval of each measurement packet, thereby measuring an available bandwidth. According to this technology, when the measurement packet train is transmitted from the transmitter terminal, the transmitting interval for each measurement packet is reduced exponentially. This exponentially increases the transmission rate for the measurement packet in the measurement packet train.
When the measurement packet passes through the network, if there is a packet of cross traffic positioned between the two measurement packets, the transmission rate for the measurement packet may exceed the available bandwidth of the network. When the transmission rate for the measurement packet exceeds the available bandwidth, the receiving interval for the measurement packet at the receiver terminal increases relative to the transmitting interval at the transmitter terminal. The technology disclosed in Non-Patent Literature 1 utilizes this characteristic, detects a point where the receiving interval for the measurement packet at the receiver terminal starts to increase in comparison with the transmitting interval at the transmitter terminal, and divides the packet size of the measurement packet by the transmitting interval at that point, thereby measuring the available bandwidth.
Moreover, Patent Literature 1 discloses a technology of causing the transmitter terminal to repeatedly transmit in plural times the measurement packet train which has a fixed size and has an equal transmitting interval to the receiver terminal, thereby searching the available bandwidth. According to the technology of Patent Literature 1, when it is determined at the receiver terminal that the receiving interval tends to increase, the transmitter terminal transmits the measurement packet train having the transmitting interval exponentially decreased to the receiver terminal. On the other hand, when it is determined at the receiver terminal that the receiving interval tends to decrease, the transmitter terminal transmits the measurement packet train having the transmitting interval exponentially increased to the receiver terminal. According to the technology of Patent Literature 1, such operations are repeated in order to perform binary searching, thereby searching the available bandwidth.